1. Field of the Invention
The present invention relates to an illumination optical system of a projection type image display apparatus; and, in particular, to a simplification of the structure of an illumination optical system suitable for a projection type image display apparatus which projects an image under magnification by using a transmission or reflection type liquid crystal display device, a digital micro mirror device DMD), and the like.
2. Description of the Prior Art
As projection type image display apparatus, those using a transmission or reflection type liquid crystal display device have been known well, for example. Also, utilization of digital micro mirror device (DMD) has recently been in progress.
FIGS. 7 and 8 are views showing configurations of conventional projection type image display apparatus using liquid crystal display devices. Each of these conventional projection type image display apparatus schematically comprises a light source unit 101, 201; an integrator unit 102, 202 for mixing luminous fluxes emitted from the light source unit 101, 201 so as to homogenize their light quantity distribution; a condenser lens 134, 234, 235 for performing a light-collecting action of this illumination optical system; and a projection unit 104, 204 for causing the luminous fluxes to carry image information and projecting these luminous fluxes onto a screen. Also, each of these apparatus comprises a plane reflection mirror 133, 233 for bending the optical path of the luminous fluxes, which are turned into uniform light by the integrator unit 102, 202, toward the projection unit 104, 204, so that each member is disposed within a limited space inside the apparatus.
Meanwhile, it is safe to state that there is always a demand for cutting down the cost when developing products in practice. The above-mentioned projection type image display apparatus are no exception.